1. Field of Invention
An aspect of the invention relates to a duct used for a projector including, for example, plural optical modulation systems for modulating plural color lights with respect to each color light according to image information to form optical images, a color composition optical system for combining the optical images modulated in the respective optical modulation systems, and a projection optical system for magnification projection of the composite optical image, and for introducing cooling air to the optical modulation systems, a cooling device, and a projector.
2. Description of Related Art
Conventionally, using a projector for a presentation in a conference, an academic conference, an exhibition, and the like is well known. Some of such projectors adopt the so-called three-plate system in which luminous flux emitted from a light source device is separated into light of three primary colors of red, green, and blue by a dichroic mirror, and the light is modulated with respect to each color light according to image information by three liquid crystal panels, and then the respective color lights after image modulation is combined by a cross dichroic prism and a color image is magnification projected via a projection lens. In the three-plate system projector, optical conversion elements, such as polarization plates for aligning polarized direction of the respective color lights to be modulated in the liquid crystal panels are provided on the luminous flux entrance side and the luminous flux exit side of the liquid crystal panel.
By the way, in the above described projector, the respective polarization plates generate heat due to application of the luminous flux from the light source device. Accordingly, in order to cool these liquid crystal panels and respective polarization plates, for example, the cooling structure as below is adopted. In other words, a cooling fan and a duct connected to the cooling fan are provided in the projector. In the duct, an entrance side air outlet for discharging cooling air to the luminous flux entrance sides of the liquid crystal panels and an exit side air outlet for discharging cooling air to the luminous flux exit sides of the liquid crystal panels are formed. By the structure, the cooling air from the cooling fan is discharged while being divided appropriately from the entrance side air outlet and the exit side air outlet, and thereby, the liquid crystal panels and the respective polarization plates can be forcibly cooled. See, for example, Publication of Japanese Patent Application No. Hei-11-295814.